United Nations, N.Y. — Raised expectations in recent weeks for Mideast peace have once again been disappointed. A hastily arranged American mediation effort between Israel and Syria may have backfired. New opportunities, which blossomed like fragile spring flowers when Israel and Jordan shifted positions on key issues, have been all but closed.
''Superpower rivalry brought an incipient regional flexibility to a halt,'' says a high Arab official.
American Secretary of State George Shultz now says there is ''a long way to go'' before an Israeli pullout from southern Lebanon can be arranged. And King Hussein of Jordan has rejected Israeli proposals to hold peace talks.
Last week, a reshuffling of political positions in the Mideast seemed to be happening as two key deadlocks - Israeli-Syrian and Israeli-Jordanian - showed signs of loosening up.
Israel, which let it be known that it was willing to leave southern Lebanon, said it no longer insisted that Syrian troops in eastern Lebanon withdraw simultaneously.
King Hussein, who severed relations with Egypt five years ago, reestablished them again. He broke ranks with most of the Arab world, which had ostracized Egypt in 1979 for signing a peace treaty with Israel.
Palestine Liberation Organization leader Yasser Arafat visited Amman the day after Jordan mended its fences with Cairo, which raised hopes that the PLO might adopt a new approach to Israel and allow Hussein to negotiate with Israel on behalf of the PLO.
Behind the scenes, Iraq, which has benefited from considerable Egyptian military aid, has also been mending its fences with Cairo. It has moved closer to forming a Cairo-Baghdad axis which moderate Arab nations such as Saudi Arabia and the other Gulf states could join later.
''White House officials saw an opportunity for a quick and easy diplomatic success to be handed to Reagan as an election plum and moved in with inopportune haste,'' says a high-ranking Western diplomat who is in constant touch with the various Middle East participants. While it is true that Israel's (Foreign Minister) Yitzhak Shamir called for a US role in mediating its pullout from southern Lebanon, no serious diplomatic preparations were made in Washington with regard to possible Syrian and Soviet moves.
''Where contact between Jerusalem and Damascus through third parties might have led to mutual understandings, the second the US entered the game, the Soviet Union showed up at the other end of the arena and pushed Syria to make maximum demands, such as an Israeli pullout from the Golan Heights as a price for its withdrawal from southern Lebanon in a way that would leave its northern border protected.''
According to an analyst at the United Nations, ''Syria is in a comfortable position vis-a-vis Israel. It can sit and wait and hope to extract more than Israel is now willing to offer. But in the end, Syria's concerns, just as Israel's, are regional and thus limited in scope. US and Soviet interests are global.
''At this juncture, each of the two superpowers wants to make maximum use of all its cards. While Syria is not merely a Soviet agent, just as Israel is not a US satellite, both are heavily dependent on their big protectors. The minute Assistant Secretary of State Richard Murphy came on the scene in the hope of pulling a diplomatic coup, so did (Soviet Foreign Minister Andrei) Gromyko, with a resounding 'nyet.' ''
A US diplomat admits: ''Even though for the first time Israelis began to praise UNIFIL (the UN interim force in southern Lebanon) and to put less emphasis on its demands that the South Lebanon Army, which takes its orders from Israel, be deployed as a buffer to protect Israel against terrorist commandos, (Syrian President) Hafez Assad advised against any conciliatory moves.''
Iraq, which also receives Soviet military supplies, may now delay its public reconciliation with Egypt at Mr. Gromyko's urgings.
As a result, incipient diplomatic movement has come to a halt and every participant in the region is back in his bunker.